1. Field of the Invention
This invention relates to lead frames having a support for a semiconductor chip and at least one lead electrically connected to the semiconductor chip, and to a semiconductor device incorporating the lead frame. The invention also relates to a method of manufacturing semiconductor devices including a lead frame.
2. Background Art
It is known to make semiconductor devices by applying a sealing resin to a side of a lead frame having a semiconductor chip thereon. Conventional CSP (chip scale packaging) technology includes SON (Small Outline Non-leaded) and QFN (Quad Flat Non-leaded) semiconductor devices. The semiconductor chips may be loaded on supports on the lead frames at predetermined intervals using heat resistant adhesive which fixes the semiconductor chips when the adhesive cures. Electrode pads on the semiconductor chips are electrically connected to multiple leads extending around the support through the use of conductive elements, such as wires. The lead frame may incorporate multiple unit lead frames which are interconnected through a tie bar network. In conventional processes, multiple semiconductor chips are mounted, wired, and simultaneously sealed. Individual semiconductor devices are then separated through a cutting operation.
This conventional technology has a number of drawbacks. With this process, the semiconductor chips and sealing resin are formed on one side of the lead frame. During a cutting process in which individual semiconductor devices are separated, the lead frame is cut together with the sealing resin by an appropriate mechanism, such as a saw blade. Since there is a difference in hardness between the lead frame and the resin, the cutting resistance varies during the cutting process. Accordingly, there is a potential problem of peeling between the resin and the unit lead frames, particularly at the leads.
Additionally, because the sealing resin adheres on only one side of the lead frame, the adherence of the resin to the lead frame may not be satisfactory. Peeling of the sealing resin may result.
In one form, the invention is directed to a semiconductor device having a unit lead frame defining a support with a peripheral edge and a first lead spaced from the peripheral edge. The first lead has a recess form therein. A semiconductor chip is provided on the support. A conductive element electrically connects between the semiconductor chip and the first lead. A resin layer is applied to the semiconductor chip and the first lead and extends into the recess.
In one form, the conductive element is a wire with an end that is connected to the first lead in the recess.
In one form, the recess extends only partially through the first lead.
In one form, there is an entry opening on the first lead in communication with the recess and the recess is configured so that solidified resin in the recess cannot be drawn through the entry opening to escape from the recess.
Resin in the resin layer may be solidified in the recess around the wire end connected to the first lead in the recess.
The recess may have a V shape in cross section, with the apex of the V located at the entry opening.
The recess may have an elongate shape.
In one form, the lead has a length and the recess is elongate and extends in a direction substantially parallel to the length of the first lead.
In one form, there are a plurality of leads in addition to the first lead spaced from the peripheral edge and there is a recess formed in each of the plurality of leads.
In one form, the support has a surface facing in the first direction to which the semiconductor chip attaches, the recess defines a first shoulder facing oppositely to the first direction, and resin in the resin layer solidified in the recess abuts to the first shoulder to prevent withdrawal of solidified resin from the recess by movement in the first direction.
The invention is also directed to a lead frame for a plurality of semiconductor devices. The lead frame has a layer defining a plurality of unit lead frames and a tie bar network interconnecting the plurality of unit lead frames. A first unit lead frame in the plurality of unit lead frames has a first support with a peripheral edge and a first lead spaced from the peripheral edge. The first lead has a recess formed therein to accept at least one of a) a conductive element which electrically connects to the first lead and b) resin which can be applied to the lead frame.
The lead frame may include a second unit lead frame in the plurality of unit lead frames, which second unit lead frame has a second support with a peripheral edge and a second lead spaced from the peripheral edge of the second support. The tie bar network includes a first tie bar connecting between the first and second leads.
In one form, the second lead has a recess formed therein to accept at least one of a) a conductive element which electrically connects to the second lead and b) resin which can be applied to the lead frame, and the recesses in the first and second leads connect to each other through the first tie bar.
The first support may have a polygonal shape, with the peripheral edge of the first support defined by a plurality of substantially straight edge portions. The one lead and at least one additional lead project from one of the straight edge portions, with the tie bar network including a first tie bar connecting the one lead and the one additional lead.
In one form, the second unit lead frame has a second support with a peripheral edge and a second lead spaced from the peripheral edge of the second support, with the first tie bar connecting to the second lead.
The second lead may have a recess formed therein to accept at least one of a) a conductive element which electrically connects to the second lead and b) resin which can be applied to the lead frame.
The recesses in the first and second leads may connect to each other through the first tie bar.
In one form, the recess in the first lead extends only partially through the first lead.
In one form, there is an entry opening in communication with the recess and the recess is configured so that solidified resin in the recess cannot be drawn through the entry opening to escape from the recess.
The recess may be elongate.
The recess may have a V shape in cross section with the apex of the V located at the entry opening.
In one form, the first lead has a length and the recess is elongate and extends in a direction substantially parallel to the length of the first lead.
The first support may have a surface facing in a first direction for supporting a semiconductor device, with the recess defining a first shoulder facing oppositely to the first direction so that solidified material in the recess is abuttable to the first shoulder to prevent withdrawal from the recess by movement in the first direction.
The invention is also directed to a unit lead frame for a semiconductor device, which unit lead frame has a support with a peripheral edge and a first lead space from the peripheral edge. The first lead has a recess formed therein to accept at least one of a) a conductive element which electrically connects to the first lead and b) resin which can be applied to the lead frame.
The recess may extend only partially through the first lead.
In one form, there is an entry opening in communication with the recess and the recess is configured so that solidified material in the recess cannot be drawn through the entry opening to escape from the recess.
In one form, the recess has a V shape in cross section with the apex of the V located at the entry opening.
The recess may have an elongate shape.
In one form, the lead has a length and the recess is elongate and extends in a direction substantially parallel to the length of the lead.
In one form, there are a plurality of leads in addition to the first lead spaced from the peripheral edge.
In one form, there is a recess formed in each of the plurality of leads, each to accept a conductive element which electrically connects to each of the plurality of leads.
The support may have a surface facing in a first direction for supporting a semiconductor device, the recess defining a direction so that solidified material in the recess is abuttable to the first shoulder to prevent withdrawal from the recess by movement in the first direction.
The invention is further directed to a method of manufacturing a plurality of semiconductor devices. The method includes the steps of: forming a lead frame having a layer defining a plurality of unit lead frames and a tie bar network interconnecting the plurality of unit lead frames, a first unit lead frame in the plurality of unit lead frames having a first support with a peripheral edge and a first lead spaced from the peripheral edge; placing a semiconductor chip on the first support; forming a recess in the first lead; electrically connecting the semiconductor chip and the first lead through a conductive element; forming a resin layer over the semiconductor chip and first lead and into the recess; and cutting the lead frame to separate the first unit lead frame, semiconductor chip, and conductive element.
The recess may be formed through an etching process.
The recess may be formed only partially through the first lead.
In one form, there is a second unit lead frame in the plurality of unit lead frames including a second support with a peripheral edge and a second lead spaced from the peripheral edge on the second support. The step of forming a lead frame may involve forming a tie bar network having a first tie bar that connects the first and second leads.
The cutting step may involve cutting through the first tie bar.
The recess may be formed as an elongate recess through the first and second leads and the first tie bar.
In one form, the lead frame has first and second oppositely facing sides, the resin layer is provided on one of the oppositely facing sides, and the process further involves applying a sealing layer on the other of the oppositely facing sides.
The sealing layer may be removed after forming the resin layer.
In one form, the first lead has a length and spaced sides and the step of forming a recess involves forming an elongate recess extending lengthwise of the first lead substantially midway between the spaced side.
The conductive element may be connected to the first lead within the recess.
In one form, the first support has a surface facing in a first direction against which the semiconductor chip is placed and the recess has a shoulder facing oppositely to the first direction. The method may further include the step of solidifying resin in the resin layer in the recess so that solidified resin in the recess abuts to the first shoulder so that the solidified resin cannot be withdrawn from the recess by movement in the first direction.